The present invention is directed toward fluid dispensing meters and more particularly to trigger release mechanisms for such devices. Hand-held devices are often used to dispense measured amounts of fluid from bulk containers. For example, automotive service stations frequently use hand-held meters to dispense small quantities of lubricating oil from large drums into automotive engines. Such hand-held meters and other similar fluid dispensing devices typically include a dispensing valve having a linearly actuated valve stem that rides within a valve cartridge. The valve cartridge is fluidly connected to a source of pressurized fluid within the device, while the valve stem is actuated by an operator to regulate pressurized fluid flow through the valve cartridge. As such, fluid can be continuously dispensed from the device so long as an operator continues to actuate the valve stem, typically through a trigger lever mechanism. In order to monitor fluid consumption, hand-held meters typically include electronics that measure and display the volume of fluid that flows through the device so that an operator is permitted to accurately dispense fluid on a job-by-job basis.
Accountability of fluid consumption is becoming a greater concern, particularly as the cost of materials such as fossil fuels continues to rise. One way of maintaining control over fluid inventories is to prevent unauthorized dispensing of fluid from hand-held meters through use of various dispensing control mechanisms, such as trigger lockouts or solenoid dispensing valves, that are remotely controlled through the meter electronics. With a trigger lockout, an electric actuator is controlled by the meter electronics, which is programmed to move a physical barrier into the path of a trigger lever to inhibit opening of the dispensing valve after a preset amount of fluid is dispensed. Trigger lockouts, however, require the trigger to be released before the physical barrier can be moved into the path of the trigger, thus permitting fluid to flow after the preset amount has been dispensed so long as the trigger remains actuated. With a solenoid dispensing valve, the meter electronics controls a solenoid valve to permit fluid flow, independently of actuation of an electronic trigger mechanism. Thus, the meter electronics can override the electronic trigger mechanism to permit dispensing only when authorized. Such solenoid valves, however, require continuous power consumption to overcome a spring force holding the valve shut, thus placing a large demand on rechargeable batteries used to power the electronics. There is, therefore, a need for an improved dispensing control mechanism, particularly for those used in fluid metering devices.